This invention relates generally to a system for use with automotive vehicle transmissions for indicating the position of the shift rod which manipulates the gear train contained within the transmission. The system has particular utility in such transmissions which include a twin clutch mechanism having a control circuit for automatically activating the clutch mechanism, the control unit being electrically fed by signals from the indication system of the present invention.
Conventional semi-automatic transmissions for use in automotive vehicles typically employ a twin-clutch mechanism which operates to decouple the transmission from the power train during gear change or selection. To achieve automatic shifting between the individual gear stages, it is necessary that the respective positions of the gear wheel pairs and/or the gear shift sleeves be recognized so as to provide for the synchronized operation of the two clutches. Thus, an object of the present invention is to provide means for controlling the twin-clutch actuation so as to permit smooth semi-automatic shifting of the gears within the transmission.
In order to attain this object, an indication system is provided within the transmission which system indicates the position of the shift rods and comprises generally a plurality of sensors fixed to the housing of the transmission in spaced relation to each other and actuating means moved by the shift rods for actuating the sensors. The sensors preferrably comprise electrical elements having a magnetic field controlled resistance. Such magnetoresistors can be actuated by magnetically conductive metal surfaces positioned adjacent the sensors by the shifting rod on which they are mounted.
In a typical transmission employing the present invention, a plurality of shift rods are present. The gear train is arranged in sets of two gears each, each two gear set being operated by a selected one of the shift rods. The plurality of sensors are arranged on the transmission housing in sets of at least three sensors, each set of sensors being responsive to two adjacent actuating means which are mounted for movement with a single shift rod. Each actuating means can preferrably operate on at least two of the sensors.
The apparatus of the present invention makes it possible to transmit electrical signals which depend upon and hence reflect the movement of the shift rods. In a twin-clutch transmission, the instantaneous engagement position of the teeth of the two gear sets is signaled during the shifting operation so that a corresponding synchronized operation of the two clutches can take place. The electrical signal is maintained until the teeth of the two-gear set is safely meshed with one another or, conversely, are safely separated from one another. Alternatively, it is also possible to effect a signal transmission at a point in time when the earliest effective torgue-transmitting engagement of the gear pair occurs. This signal transmission, beginning at the preliminary engagement and continuing through the final engagement of the gear set, ensures smooth automatic shifting from one gear to the other gear within the transmission.
Additional features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of an illustrative preferred embodment exemplifying the best mode of carrying out the invention as presently perceived. The detailed description particularly refers to the accompanying figures.